화학공학소재연구정보센터
Separation Science and Technology, Vol.39, No.13, 2931-2949, 2004
A new tangential streaming potential setup for the electrokinetic characterization of tubular membranes
A new electrokinetic setup was developed for assessing the active layer zeta-potential of tubular membranes based on tangential streaming potential and electrical resistance measurements. Although the flow was not wholly laminar (because of the large hydraulic diameter of channels), the electrokinetics theory could be used to convert the streaming potential data into zeta-potentials because the electrical double layer lay within a laminar sub-layer near the channel walls. Electrical resistance data allowed for the account of the conduction phenomenon through the membrane porous body. The new device was tested over a range of pH with a tubular ceramic membrane composed of three channels with a titania active layer. The isoelectric point was found to be in good agreement with that determined from salt retention data. The zeta-potential value determined at pH = 3.5 using the present device was compared with that obtained on a flat membrane made of the same material using the traditional microslit electrokinetic setup. A good agreement between the two measurements was observed. It was shown that neglecting the electric conduction phenomenon through the membrane porous body leads to a low underestimation of the zeta-potential (less than similar to20%). This is related to the large size of channels. The contribution of the membrane porous body was found to be independent of the pH of solution. This suggests that the support layer of the membrane would make a decisive contribution to the electric conductivity of membrane porous body.